There is disclosed a display device using a color wheel having a color filter Cw, in addition to normal color filters corresponding to the three primary colors. The filter Cw has almost flat spectral transmission characteristics. Brightness information included in a color image signal is quantized with (n+m) bits. Information corresponding to the lower-order n bits is displayed by light transmitted through the filter Cw. Information corresponding to the upper-order n bits is displayed by light transmitted through the normal color filters. Only brightness information to which the human eye is visually sensitive is reproduced by the filter Cw having a lower transmissivity. This can eliminate a lack of the number of gray levels due to a constraint on the minimum switching speed of a light valve. Furthermore, the brightness little deteriorates.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A display device for displaying an image according to input image data that is digital data, said display device comprising: a light source for producing light; light-transmitting filters for separating the light from said light source into at least four kinds of light including white light, said light-transmitting filters including a white-transmitting filter for transmitting white light and non-white transmitting filters; a light valve for projecting each kind of light from said light-transmitting filters onto a screen; said white light-transmitting filter being used to display information corresponding to lower-order bits of said digital data; a signal converter portion to control said white light-transmitting filter using a control signal corresponding to said lower-order bits, said signal converter portion including input terminals for receiving non-white light signals and a brightness signal calculating unit for calculating the brightness of the non-white light signals; said non-white light-transmitting filters being used to display information corresponding to said higher-order bits of said digital data; a drive device directly coupled to said signal converter portion for creating control signals for controlling the light transmitting filters and light valve; and an integrated value of a transmissivity in a visible range of said white-transmitting filter is smaller than the combined integrated values of transmissivities in a visible range of said non-white transmitting filters; wherein brightness created by a first gray level represented via said white light-transmitting filter is ½ m (m is the number of lower-order bits) the brightness created by a first gray level represented via said non-white light-transmitting filters.
2. The display device of claim 1 , wherein said white light-transmitting filter has spectral characteristics that are almost flat in the visible range of wavelengths of the light.
3. The display device of claim 1 , wherein if a brightness required by the input image data is lower than a given gray level, information is displayed using said white light-transmitting filter or said non-white light-transmitting filters, and if said brightness is higher than said given gray level, information is displayed using only said non-white light-transmitting filters.
4. The display device of claim 1 , wherein said light valve is of the reflective type.
5. The display device of claim 1 , wherein said light valve is of the transmissive type.
6. The display device of claim 1 , wherein a value obtained by integrating the product of spectral transmission factor of said white light-transmitting filter in the visible range and spectral luminous efficiency with respect to wavelength is less than sum of values obtained by integrating the product of spectral transmission factor of each of said non-white light-transmitting filters in the visible range and spectral luminous efficiency with respect to wavelength.
7. The display device of claim 1 , wherein said signal converter portion controls said non-white light-transmitting filters using another control signal corresponding to said higher-order bits.
8. A method for displaying digital image data from a display device, comprising: decomposing light from a light source into a plurality of colors, one of said plurality of colors being white; controlling a white-light transmitting filter of a set of filters with a control signal corresponding to lower-order bits of said digital image data generated by a signal converter portion, wherein said signal converter portion includes input terminals for receiving non-white light signals and a brightness signal calculating unit for calculating the brightness of the non-white light signals; controlling, by a drive device directly coupled to said signal converter portion, the light transmitting filters and a light valve used to project light from the set of filters; displaying information corresponding to said lower-order bits using said white-light transmitting filters; and projecting said plurality of colors from said set of filters; wherein an integrated value of a transmissivity in a visible range of said white-light transmitting filter is smaller than the combined integrated values of transmissivities in a visible range of the other filters in said set of filters; wherein brightness created by a first gray level represented via said white light-transmitting filter is ½ m (m is the number of lower-order bits) the brightness created by a first gray level represented via said non-white light-transmitting filters.
9. The method of claim 8 , further comprising displaying information corresponding to higher-order bits of said digital image data.
10. The method of claim 9 , further comprising controlling non-white transmitting filters of said set of filters with another control signal corresponding to said higher-order bits of said digital image.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
January 12, 2000
June 28, 2005
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